The present invention relates generally to gas turbine engine blades, and more specifically, to a blade having a dovetail including fillets and means for reducing total stress therein.
Conventional blades used in gas turbine engines include dovetails for retaining a blade in the outer circumference of a rotor disk. The dovetails may be symmetrical or asymmetrical and typically include circumferentially spaced lobes which fit into a complementary channel disposed in the perimeter of the turbine rotor disk to retain the blade. The dovetail lobes are connected to an airfoil portion of the blade through a shank and at the intersection thereof is typically formed a neck fillet. The fillet is an arcuate surface typically as a portion of a circle of a given radius and has values which are made as large as possible within physical constraints to reduce the concentration of stress thereat.
More specifically, a gas turbine rotor blade is subject to substantial centrifugal loading forces which generate tensile stresses in the blade. The centrifugal loads must be resisted by the dovetail secured to the rotor disk. The tensile stresses in the blade are also found in the dovetail and are necessarily concentrated at the fillets as is conventionally known. The fillets are therefore limiting factors in the design of the rotor blade since the stress at such fillets must be maintained at acceptable levels.